Soluble adenylyl cyclase links Ca(2+) entry to Ca(2+)/cAMP-response element binding protein (CREB) activation in vascular smooth muscle

Ca(2+)-transcription coupling controls gene expression patterns that define vascular smooth muscle cell (VSMC) phenotype. Although not well understood this allows normally contractile VSMCs to become proliferative following vessel injury, a process essential for repair but which also contributes to vascular remodelling, atherogenesis and restenosis. Here we show that the Ca(2+)/HCO(3)(−)-sensitive enzyme, soluble adenylyl cyclase (sAC), links Ca(2+) influx in human coronary artery smooth muscle cells (hCASMCs) to 3′,5′-cyclic adenosine monophosphate (cAMP) generation and phosphorylation of the transcription factor Ca(2+)/cAMP response element binding protein (CREB). Store-operated Ca(2+) entry (SOCE) into hCASMCs expressing the FRET-based cAMP biosensor H187 induced a rise in cAMP that mirrored cytosolic [Ca(2+)]. SOCE also activated the cAMP effector, protein kinase A (PKA), as determined by the PKA reporter, AKAR4-NES, and induced phosphorylation of vasodilator-stimulated phosphoprotein (VASP) and CREB. Transmembrane adenylyl cyclase inhibition had no effect on the SOCE-induced rise in cAMP, while sAC inhibition abolished SOCE-generated cAMP and significantly reduced SOCE-induced VASP and CREB phosphorylation. This suggests that SOCE in hCASMCs activates sAC which in turn activates the cAMP/PKA/CREB axis. sAC, which is insensitive to G-protein modulation but responsive to Ca(2+), pH and ATP, may therefore act as an overlooked regulatory node in vascular Ca(2+)-transcription coupling.